The correct answer is B) to the steam connection, but not water connection. The reason for this is that the steam connection on a single-element feed water regulator needs to be properly lagged (insulated) to prevent heat loss and maintain the proper operating temperature. However, the water connection does not need to be insulated, as the temperature of the water is not as critical to the proper functioning of the regulator. The other options are incorrect because: A) only insulating as necessary to prevent injury is not the proper way to lag the regulator, C) insulating both connections including finned areas is unnecessary, and D) insulating the water connection but not the steam connection would not properly maintain the operating temperature of the regulator.